Salam, Merry.

Thank you for your question.

The day of Eid al-Adha is known the world over as "Al-Eid Al-Kabir", or the Major Feast. It is distinguished from "Al-Eid Al-Saghir", which is the Minor Feast, known also as Eid al-Fitr. This is actually celebrated by Muslims two months and ten days before the Major Feast.

The word "Eid" means a recurring festival. The name of Eid al-Adha means the Feast of Sacrifice. It is celebrated on the tenth day of the lunar month of Dhul-Hijjah.

On the ninth day of Dhul-Hijjah, pilgrims proceed to the plains of the Mount of `Arafah, outside Makkah and they spend their time totally in worship. This is the core of the worship of Hajj, without which no Hajj is said to have been performed. On that evening, pilgrims proceed from Arafah to Muzdalifah.

Early in the morning of the 10th day of Dhul-Hijjah, the pilgrims having offered their prayers at Muzdalifah, proceed to the three pillars to cast seven stones at the symbols of Satan. This ceremony of casting stones has been performed since the days of Prophet Ibrahim (Abraham) (peace be upon him).

It is a ceremony which indicates that one should cast away the evil of Satan repeatedly and resolve never to listen to him again, nor to succumb to temptations. In fact, the word for the casting process in Arabic is "rajm", which means throwing of stones.

Then, pilgrims return to Mina, with a pure slate of mind and heart, where they perform the sacrifice of animals. This process commemorates the event when Prophet Ibrahim was about to sacrifice his most beloved treasure, his son…

It was his only son, whom he begot in old age after sincerely having implored Allah, for a son for a very long time. It was Ismail--his beloved and righteous son--who was destined also to become a prophet. He is known as "Adh-dhabih", or the chosen sacrifice of Allah.

Hajj is, in fact, considered a re-affirmation of the faith of Prophet Ibrahim, whom is considered the "father" of all prophets.

For those who did not go to Hajj, this year--like most of us--it is celebrated as a feast. We begin with the prayers of Eid, following which, sacrifices of animals are made and the meat is shared with the poor.

It is a pity that over scores of years, the act of sacrifice has lost its meaning. It has become a mere ritualistic performance among Muslims who sometimes slaughter goats, sheep and cows annually and mechanically, without understanding the underlying significance.

There is a difference between mere charity and sacrifice. Charity is a regular all-time practice of helping the needy and no particular day is fixed for it. This is while sacrifice is an annual ritual, which is to be performed on the prescribed days commencing with Eid al-Adha.

Thank you and hope the answer is satisfying.

Salam.

Useful Links:

Understanding the Why of Hajj

What You Should Know About Hajj

Spiritual Ethics of Hajj

Once in a Lifetime 

Hajj… a Journey of Spiritual Healing

Honor the House, Kiss the Stone?

From One to Ten … All Merits!

A Stand of Forgiveness

The Black Stone… an Idol?

Rejoicing the Sacrifice

Takbir of Eid